The present invention relates to an improved microorganism culturing dish, commonly referred to as a petri dish. More particularly, the present invention is directed towards an improved petri dish, with several newly provided and improved characteristics. The petri dish of the present invention is, relative to the prior art, less expensive to produce, uses less materials, is easily stackable, and provides both unexpected results with respect to the even distribution of the culturing media during manufacture and increased shelf-life.
Prior art petri dishes generally include a bottom container and a mating cover member. The bottom container usually takes the form of a shallow truncated cylinder, while the cover member likewise takes the form of complementary truncated cylinder having a somewhat enlarged inside diameter to allow the cover member to fit over the bottom container.
Although the structure of a petri dish is quite simple, it must perform its intended function as efficiently and inexpensively as possible. Ideally, the petri dish should be a shallow rigid container which is easily manipulable by a technician with respect to manual placement and removal of the cover member. Also, the petri dish should efficiently receive and distribute liquid nutrient media during the manufacturing process so that a uniform layer of solidified media with a continuous meniscus with the side wall of the bottom container is obtained. In this regard, the interior configuration of the bottom container should not impede the distribution of the liquid nutrient media during filling. For example, it is known to provide machinery that physically wobbles the bottom container during filling to assist in the even distribution of the liquid media prior to hardening to form the media layer on the bottom of the container. Further, the dish must be susceptible to stacking, the stacked dishes interrelating with one another sufficiently to permit convenient transport in the stacked configuration.
Examples of prior petri dishes are contained in the following U.S. Pat. Nos.: 4,160,700 to Boomus et al; 3,198,713 to McCormick; and 3,649,463 to Buterbaugh. The Boomus dish has a radial flange on its lid to facilitate single-handed manipulation for removal of the lid, and a mating arrangement between a lid and the bottom surface of a petri dish stacked thereon. The McCormick petri dish, on the other hand, is a lid-less system. McCormick proposes the stacking of several bottom members such that each successive dish provides a lid for the preceding dish in the stack. Buterbaugh is similar to Boomus in that the Buterbaugh dish and its features are directed towards ease of manual manipulation of the disk. As such, Buterbaugh discloses a dish bottom portion having an outwardly extended peripheral flange with a series of inwardly extending slots. The flange is configured so as to facilitate manual grasping the dish.